Hydraulic apparatus



4, c. E' ADAMS HYDRAULIC APPARATUS Filed March 28. 1947 TO SYSTEM 42/ 43 42 30 2/5 28 36 'fk Q\ 2 O 26 A ff 34 35 37 4o 3e l /l 2 Y-D /55 r #wd-4? j' J V 46:; k

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MMM@ FRMUMP -55 57\ f INVENToR. CECIL E. ADAMS BY l Patented Apr. 4, leso UNITED STATES PATENT QFFICE i Denison Engineering Company,

Columbus,

Ohio, a corporation of Ohio Application March 28, 1947, Serial No. 737,932

This invention relates generally to the science of hydraulics and is particularly directed to fluid pressure energy translating devices of the type employed in the transmission of motion and power. More specically this invention is directed to volume control mechanism for a fluid pressure energy translating device of the type having an element which is movable to vary the volume of uid discharged by the device.

An object of this invention resides in utilizing an intentionally created pressure differential to regulate the volume of fluid delivered by a pump so that the control mechanism for the pump may be remotely located therefrom.

Another object of the invention is to provide a pump with a movable member for varying the volume thereof and a plurality of fluid pressure responsive elements for imparting movement to the member for varying the volume, the pump being further provided with means for restricting fluid flow to create a pressure differential, the contrasting pressures being applied to the fluid pressure responsive elements to move the volumevarying member to and retain the same in a position to cause the pump to deliver a predetermined volume of fluid.

Another object of the invention is to provide a fluid pressure energy4 translating device which functions as a pump, with a volume-varying member mounted for movement and providinga pair of oppositely actingpressure responsive elements in the form of pistons to move the volume-varying member in opposite directions, one of the pistons being supplemented by a resilient power-transmitting element in the form of a spring which tends to move the volume-varying Vmember toward a predetermined position, the

device also being provided with a flow-resisting element to create a pressure differential which is applied to the pistons to move the volumevarying member in opposition to the spring so that the volume produced will be controlled by the pressure differential.

Another object ofthe invention is to provide i to deliver the volume necessary to maintain the pressure differential.

A further object is to dispose the flow-resisting element mentioned in the two preceding paragraphs, in the outlet line of the pump so that 1 Claim. (Cl. 103-161) the entire output thereof will be exposed to the action of the element and thus a more accurate control of the pump volume will be secured.

A still further object is to provide an automatic throttle or now-resisting element which includes a metering spool, a device for resiliently urging such spool toward a certain position and means for subjecting the spool to fluid pressure to move the same in opposition to the urging means to maintain a uniform pressure drop or differential which is utilized-to effect a pressure adjustment of the volume-varying member of the pump and the development of constant horsepower by motor units supplied with fluid by the pump.

In the drawings:

Fig. 1 is a diagrammatic view of a radial piston pump provided with a volume control formed in accordance with the present invention.

Fig.l 2 is a similar view of an axial piston pump provided with a control mechanism formed in accordance with the invention; and,

Fig. 3 is a diagrammatic view of an automatic throttle which may be employed in carrying out the invention. A y

Referring more particularly to the drawings and especially to Fig. 1, the numeral 20 indicates generallyl a radial piston pump; this pump is of conventional form and includes a pintle 2| about which a cylinder barrel 22 revolves, the pintle being provided with oppositely disposedA recesses 24 and 25, the former communicating with inlet passages 26 while the latter communicates with outlet passages 21. The cylinder barrel 22 has a plurality of radially extending chambers 28 which alternately communicate with the slots 24 and 25 as the cylinder barrel is revolved, suitable mechanism, not shown, being provided to cause such movement of the cylinder barrel. The chambers 28 receive, for sliding movement, piston elements 3U which are provided at their outer ends with rollers 3| for engaging the inner surface of an adjustable ring 32, suitable means, not shown, being provided for maintaining the engagement of the rollers with such ring.

The ring is disposed for adjustment within a i casing 33 to vary the relation of the ring and pintle members to one another, the ring being movable from 'a position in concentric relation to one of eccentric relation to the pintle member. When the ring is concentric with the pintle the cylinder barrel may be revolved without effect, the pump then being said to be operating at zero volume. When the ring is moved to the maximum degree of eccentricity relative to the pintle 'plate 48.

the pump will be operating at a maximum volume; it is urged toward this position by a spring 34 disposed in the casing between a piston 35 and the end of a chamber 3S in which such piston is arranged for sliding movement, this chamber 36 being located at one side of the casing 38. By locating the ring 32 in eccentric relation to the pintle and rotating the cylinder barrel 22 in the direction of the arrow 31 in Fig. 1, pistons 30 will be moved into and out of the cylinders 28 causing a transfer of fluid from recess 24 to recess 25. The amount of fluid transferred and consequently the volume of fluid delivered by the pump will be varied by changing the degree of eccentricity of the ring 32.

To effect movement of the ring toward a concentric position the casing 33 is provided on the side opposite the chamber 35 with a second chamber 38 in which a second piston 40 is disposed for sliding movement. Pistons 35 and 40 are suitably engaged or connected with the ring 32. To cause the piston 40 to move the ring 32, fluid under pressure is introduced into the outer end of the chamber 38. This fluid is conducted to the chamber through a line 4| which is connected with the outlet line, indicated by the numeral 42. of the pump. This line 42 communicates with the passages 21 and at a point beyond the connection of the line 4i therewith, it is provided with an orifice or adjustable restriction 43, this restriction serving to resist the flow of fluid through the line I42 to cause a pressure drop thereinv at opposite sides of the restriction.

A second line 44 extends at the down-stream side of the orifice 43 and the outer end of the chamber 35. This arrangement subjects pistons 35 and 40 to the contrasting pressures of' the pressure differential created in the outlet of the pump by the orifice 43. When the orifice is adjusted to provide a minimum restriction, a large volume will be necessary to create the pressure drop, spring 34 will consequently move the ring 32 to cause the pump to deliver a greater volume of fluid. If it is desired to reduce the volume the orifice 43 is adjusted to offer more restriction Since a smaller volume will produce the pressure drop the pressure in line 42 will increase and be supplied to chamber 38 through line 4I. The ring will then be moved in opposition to the spring 34 until the force of the spring 34, plus the fluid presiure in back of piston 35 equals the fluid pressure in the chamber 38. With this arrangement the orifice 43 and the means for adjusting the same may be located remotely from the pump at any suitable point of control.

In Fig. 2 the invention has been applied to an axial piston pump 45. In this type of pump the pistons 46 are moved into and out of the cylinder barrel 4l by an inclined cam or swash To vary the volume of fluid delivered by such pump, the swash plate 48 is made adjustable about en axis extending at right angles to the axis of rotation of the cylinder barrel 41. To ell'ect the movement of the cam plate 48 the casing of the pump is formed with a pair of chambers 50 and 5I on opposite sides of the pivotal axis of the plate 48. The chambers 50 and 5I receive, for sliding movement, piston elements 52 and 53, the chamber V5i) also receiving a coil spring 54. This spring tends to urge the cam plate 48 toward a maximum inclined position whereby the highest volume of fluid will be delivered by the pump.

between the line 42 To vary tho position of the cam plate 48. chamber 5i ls supplied with fluid under pressure. This fluid is taken from the outlet line 55 of' the pump immediately in advance ol' an adjustable orillee 58 disposed in such line. The fluid is transmitted from line 55 to chamber 5| through u brunch line 51, the 'pressure ol this fluid acting upon piston 58 to effect the movement oi' the plate 48. Spring 54 is supplemented by fluid pressurll introduced into eiuunber 50 through a lino 58 which is connected with line 55 on the low-pressure side of' the orifice 56.

In both forms of the invention, the pressure from the high pressure side of un orifice is applied to n piston to shift the volume control mechanism in u. direction to reduce the volume. This movement of the control mechanism is opposed by another piston which tends to move the control mechanism in the opposite direction, this second piston being exposed to the pressure from the low-pressure side of the orifice. The second piston is assisted by a spring and the pressure drop caused by ihe orifice is such that the total l'orcc of the spring and the pressure applied to the second piston will balance the force of the pressure applied to the first piston so that the volume control mechanism will be held in a selected position to deliver a predetex-mined volume. When the orifice is adjusted, thc balance of the forces acting upon the volume control mechanism is temporarily disturbed and th'.` volume control mechanism will be operated to tend to restore such balance. If the orifice is reduced, the volume control mechanism is operated to lower the volume delivered by the pump; if the orifice is enlarged. the volume must be increased to restore the balance.

From the foregoing discussion of the two forms of the invention shown in the drawing it will be obvious that the position of the volume-varying member of a pump provided with the control mechanism will be dependent upon an orice in the outlet line, the volume bearing a direct relation to the size of the orifice.

Fig. 3, in the drawings, discloses an automatic throttle which may be used in the volume control system as a constant-horsepower control for a. fluid pump. In prior apparatus for automatically controlling fluid pumps, use has been made of so-called pressure centering controls which operated to maintain the volumetric delivery of the pump controlled thereby until a given pressure was reached and then suddenly reduced the volume until only sufficient fiuid was delivered to maintain the pressure. With such a mechanism the horsepower developed by the motor driving the pump fluctuated according to the pressure variations and a motor having the maximum capacity required at any time was neces-v sary. With the automatic control shown by applicant in Fig. 3, a uniform horsepower will be developed regardless of the change in pressure, the volume being automatically varied to maintain the horsepower required.

The device shown diagrammatically in Fig. 3 includes, a body 6D having a chamber 6| for the slidablereception of a metering spool B2. This spool is formed with an external groove 63 having atapered shoulder 64 at one end; this tapered shoulder moves when the spool is adjusted, relative to an annular groove 65 formed in the body 60. This groove is connected with the outlet line 66 leading from a suitable pump the volume of which is to be controlled. Another line 61 leads from the chamber 6I in spaced relation from the groove 65, the line 61 being in registration with the groove 63.

The spool 62 is normally urged toward a position to provide open communication between the groove 65 and the line 61, by a coil spring 68 positioned between the spool 62 and an adjustable spring abutment 70, this member being operated by a manual control 1I. A branch line 12 leading from the line 66, extends to the volumereducing piston 4U or 53 of a pump of the types shown in Figs. .1 or 2, While a second branch line 13 extends from the line 61 to the volumeincreasing piston of such a pump. Line 13 is also connected with the chamber 6| of the automatic throttle mechanism. at the end of spool 62 opposite that engaged by spring 68. The spool 62 will thus be moved in response to pressure existing on the outlet side of the automatic throttle. If the pressure tends to increase, spool 62will be moved to restrict uid ow from groove 65 to passage 61; if such pressure tends to fall. spool 62 will move to facilitate fluid ow between groove 65 and line`61.

When the pressure varies, due to conditions in the system supplied by the pump the balance of pressures on the pistons of the volume control mechanism is temporarily disturbed and the volume is changed in a manner tending to restore the balance. The volume changes gradually and the horsepower developed by the driving motor remains constant.

I claim:

In a variable Volume iluid pump, an inlet; an outlet; piston and cylinder means for transferring fluid from said inlet to said outlet; a movable volume varying member; means tending to yieldably urge said volume varying member toward a maximum-volume position; throttle means in the Aoutlet of said device, said throttle meanshaving an inlet connected with the outlet of said pump and an outlet; a metering valve between said inlet and outlet; means yieldably urging said valve toward an open position; means for applying outlet pressure of said throttle to said metering valve to move the same in opposition to said second-mentioned urging means; opposed pressure responsive elements operative to impart movement to said volume varying member, one of said elements moving said member in opposition to the first-mentioned urging means; and means for applying the outlet pressure of the pump to said one element and the outlet pressure of said throttle means to the other of said elements.

CECIL E. ADAMS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS I Number 

